A first technology is proposed that guarantees a constraint parameter such as a unique constraint of a database (hereafter, “DB”). In the first technology, counters are employed to count violations that occur and violations that are cleared at a given level (for example, per transaction) during DB operations, and when the value of the counter for each constraint parameter is 0 at the end of the given level, it is determined that there are no violations.
In a second technology, when DB difference information is entered into a difference table in preparation for undo processing, in cases in which plural items of difference information exist for the same primary key or for the same entry or attributes of a directory, only the first of such data is saved in a difference table. The second technology makes use of the fact that when plural items of difference information for the same primary key or for the same entry or attributes of a directory are sequentially entered into a difference table, the entry of a second, or subsequent, item of difference information will result in a primary key constraint violation.